Lightweight containers

I've been toying quite a bit with Vagrant + Puppet, which allows me to develop Puppet provisioning manifests/modules in a fairly comfortable way... except that it's slower than I like.

I'm looking into ways of accelerating this. First thing I'm looking into is mirroring/caching of downloads, which shouldn't be very problematic.

The other direction I'm thinking of is replacing VirtualBox with something lighter. I've seen some work done on using LXC with Vagrant, but it seems to be in a very early stage (there seems to be little RHEL/CentOS support, for instance). I'm thinking I don't really need Vagrant (Vagrant's nice because it automates some stuff in VirtualBox, but I think that shouldn't be so complicated on LXC/OpenVZ/whatever), but I'm not sure. I've been playing with virt-install, but LXC support seems to be iffy.

Has anyone found a good option for lightweight spinning up of Debian/Ubuntu/CentOS? LXC? OpenVZ? VServers? I thought about going back to chroots even...